Eureka I Have Found It

"Eureka!" — "I have found it!" — was attributed to Archimedes by the Roman architect Vitruvius in De Architectura, Book IX (c. 15 BC), written roughly two centuries after Archimedes lived. According to the story, King Hiero II asked Archimedes to determine whether his new crown was pure gold without melting it down. Archimedes realized, while stepping into a bath, that an object displaces water equal to its own volume — allowing him to compare the crown's density to that of pure gold.